Process for returning and recovering heat from vapors produced in alpha process of decomposing petroleum oils



Dec. 1, 1931..

COIZHEIT-SE R A. STROUT 1.834228 PROCESS FOR RETURNING AND RECOVERING HEAT FROM VAPORS PRODUCED IN A PROCESS OF DECOMPOSING PETROLEUM OILS Filed Sept. 26, 1927 E v E 2 6 E R3 Cum-155 DIST/LLI/VG l HPO RI 2 n 1/0 DEPHL EGNFITO R CHAHBER FUR/Y4 CE arm/M4 4 Patented Dec. 1, 1931 3 UNITED v STATEs PAT ENT. OFFICE ARCHIE L. STROUTQOEBERKELEY, CALIFORNIA, 'ASSIGNOR *ros'rAimAnD 011.com-

DELAWARE PANY or CALIFORNIA, I or SAN FRANCISCO, oA mormL A conron 'rron OF PROCESS FOR RETURNING AND REGOVERING IIEAT FROM 'VA PORS PRODUCED IN A i IIE'IlEKJOCESS OF DEOOMPOSING PETROLEUM: OILS Application filed September 26, 1927. SerialNo; 221,920.

This invention relates to the art of decomposingor cracking oils, such as petroleum oils, and has to do more particularly with a cracking process commonly known as the vaporization type wherein. the charging stock, after passage through the-heating zone in which the oil israised to the desiredcracking temperature, passed .into' an. enlarged "reaction chamber where vaporization takes 10 place for the separationof the lower boiling point constituents ff'ror n those of higherfboilingpoint.

f Heretoforain the practicejof thevaporiza- 7 stages of distillation. which take place infa tion method of cracking oils asj above, outlined, therehas been evolved from the vaporization chamber not only those constituents comprising the d gaired low boiling" pointv or gasoline like pro sets, but in addition thereto, so inuehof th' heavier or higher boiling point ingredients. thatthere isleft in the vaporization chamber either only coke-or a heavy liquid residuum oflow A. P. .L gravity, usu'ally at about 9 A. P. I. gravityor such as to make it of suitable fuel oilviscosity. hen the proc'essfis thus practicedthe total vaporized material from the vaporization'chamber is'passed to a dephlegmating towerin which the heavier vapors are condensed from the gasoline-like or desired low boiling point ingredients, and such heavy constituents therefrom recycled as a reflux from the tower. back through the heating coils and into the vaporization chamber.

In the co-pending application of Ralph A. Halloran andArchie L. Strout, filed March 21,1927, Serial No. 176,990 process ofde composing relatively highboiling point oils into relatively'low boilingpoint oils, there is described a type of crackingprocess of the vaporization type in which, in order to se-' cure asubst antial reduction in the quantity of coke formed in the process and substantial reduction in the sediment content ofthe liquid residuum produced in the process, as

A. P.,I. gravity several degrees higher than thesy'stem and in. fact but slightly less in the. vaporization chamber and the said reflux' may be returned to the well as other advantages, the liquid in the vaporization chamber is maintained at an charged to the system. In order to obtain a high yield of gasoline-like or low boiling point constituents, itis necessary that the lower boiling point oils which are contained within this liquid thus withdrawn fromthc c vaporization chamherpand Which are useful for further cracking, be distilled therefrom and recycled through the processj It is the' practice of said co-pending application this to separate and use such lower boiling 'point constituents from this liquid withdrawn from In order to distinguish between. thetw o system of this typeit will he understood that throughout the following discussion the g zone of the system" and whereinthe prothere. will be evolved along with saidivapors the vaporsof certain heavier constituents,

thus making, it necessary toufractionatethese vapors so that the gasoline-like constituents' may he separated from the heavier constituents. The term dephlegmator as used herein will be restricted to refer only to the fractionating equipment wherein this separation takes place. The term reflux will be restricted to the condensateobtained in said dephlegmator and returned to the heating'zone. The material obtained by the condensation of vapors evolved during the distillation of the liquid withdrawn from the aforesaid vaporihs zation chamber will be referred to as cycle stock and the vapors condensed to give said cycle stock will be termed cycle stock vapors. (It will be noted that both the said cycle stock .0 heating zone of the system.) The bottoms remaining from the evolution of the cycle stock vapors will be'termed residuum asdistinguishedfroin thebottoms withdrawn from Y the aforesaid vaporization chamber, which"="06 latter material will be designated as-heavy liquid .from' the vaporization chambers j the gravityof the residuum tojbe formed in In'orderto completelycondense the cycle stock vapors, it-is generally" necessary that they be'cooled to about-250 to v300 F Lln-i i Heretofore, in attempts to preheat feed oi of a crackingsystem, the common practice has been to utilize as far as practical heat exchangers so' constructed thatthe liquid feed oil to be heated passes through closed pas- I sages in contact with the opposite walls of (Strout filed April25, 1927, Serial No'."186,30 7, process of decomposing relatively high bo1lwhich is the medium to be cooled. Heat exchangers for this purpose are expensive to build and maintain. These, together with various other disadvantages, result in the fact that comparatively few heat exchangers are successfully employed to eifect economy .in connection with cracking apparatus.

In another co-pending application of A. L.

ing point oils into relatively low boiling point oils, is described a process by which the recovery of the heat'of the cycle stock vapors may be accomplished by transfer of heat to I the fresh feed stocktovbe processed. This is done by the; use of direct'contact between the vapors of the oil to be recycled and the fresh oil. Inorder to maintain .economicaloperation it isnecessary not only that the heat of the cycle stock: vapors be preserved, but it is also necessary to conserve the heat in the vapors from which the reflux material is In order to form the desired amount of reflux in it necformed in the dephlegmator.

essary that there be employed a coolingmedium, the temperature of which may-vary within certain limitsxdepending upon the quantity of material so used. The present invention comprehends a process in which the heat of the cycle stock vapors may be recovered and imparted to the feed oil while i at the same time using the heated feed oil and the resulting cooled cycle stockmaterial, or different portions thereof, to maintain a cooling medium in the dephlegmatorsufficient to form the desired reflux.

v An:o bject of the present invention'is to provide a method or process for recovering :the useful heat in a vaporized oil which is to becondensed and recycled to a cracking i process, and a'particular object of the present invention is to. provide a method by which: the recovery of the heat of the cycle stock vapors maybe accomplished by transfer of heat to the fresh feed stock to processed. I g I Another objectof the present invention is r to provide a method for eflicientlyrecovering the heat of thecycle stockvapors, which employs the use of directcontact between the the I vaporization cham Vapors of the oil to be recycled and the fresh oil.

Another object of the present invention is to provide amethodfor condensin and recovering the heat of'the cycle'stoc vapors using condensed cycle stock and fresh feed oil for this purpose, and using this combined cycle stock and feed oil, or a part of' it, as a refluxing agent in the dephlegmating tower of the system.

Another objectof the pment invention is vto provide a process of the class described in which the necessity for a multiplicity of recycling pumpsv and. condensing and exchanging equipment is avoided.

Another object of the present invention is to provide a method for recovering the heat of the cycle stock vapors and the substantial condensation thereof by direct contact with a portion of the fresh feed oil, an'd'by pre cooling such hot cycle stock vapors by passage through a closed type heat exchanger counte rcurrent to the commingled feed stock and; condensed cycle stock By the process of the present inventionthe oil to be cracked is passed through a heating coilwhere it is raised to a high temperature and pressure and thenpassed into a vaporization chamber where vapors are allowed to separate. These vapors then flow through a dephlegmator to awater-cooled'eondenser and receiving tank, all held at super-atmospheric pressure.' The li uid withdrawn from r is permitted to evaporate in partrby releasing the pressure. The portion which fails toevaporate at this reduced pressure'is withdrawn from the system as low-sediment residuum. The vaporized portion (i. e. the cycle stock) is passed through 'a closed heat exchanger where it gives up a part of its heat and where, as a:

consequence, some of it is condensed. This cycle stockthen enters a chamber in which the vaporous portion is contacted with and.

condensed by a spray of cool feed stock.

'Combined feed stock and condensedcycle stock are pumped from the bottom, of the aforementioned chamber through a closed passage in a heat exchanger, in contact with theopposite walls of which is the hot cycle stock vapor. The mixed'feed and cycle stock 7 is thereby further raised in temperature and flows back to the heating coilto be again subjected to cracking conditions. The present invention may .beibetter understood and comprehended in its various aspects in connectionwith the'description of a process comprising an embodiment of the inventlon, by reference to the-accompanying-- drawings which illustrate an apparatus in which a process embodying the" invention may be performed. For'this purpose-there is hereinafter described a process-embodying the present invention as carriedv out with chamber 1.

the apparatus illustrated in the accompanying drawings. p

In the drawings, the apparatus is trated in diagrammatic elevation.

a In the drawings, lrepresents a heating coil illusset in a furnace 2. In this coil the oil is raised to the desired decomposing temperature.

Any decomposing temperature may be em ployed, a particularlysuitable temperature being from 850 to 890 F. when processing a gas oil fraction of California base oil. The

temperature may be modified, depending upon the character of oil processed as well as the quantity and quality of the-products to be produced. Itis then passed through line 3 into a vaporization and reaction The pressure employed within the vaporization chamber will depend on the oil treated and the amount of decomposition and vaporization of the heavy oils desired, but will generally range from 200# upwards, per square inch. From the vaporization chamber 4 the vapors pass through vapor line' 5 into a dephlegmating tower 6 which may be one of several diflerentlandsuitabl'e type In this dephlegmating tower the desirable lighter or gasoline-likeconstituents will be separated from the heavier constituents and will pass in vapor form through line 7 and thence through sultable condensing apparatus such,

for example, as condenser coil 8. The condensate thus formed then passes throughline 31 into receiving drum 9 where anyrel'at-ively fixed or incondensable gas is permitted to separate therefrom. This gas may be led off through valve 11 and line and conducted from the system. The condensed gasolinewill comprise a quantity of material whose boiling points are higher than those of the "constituents vaporized in the vaporization chamber 4:. However, this material may be used as a cycle stock for further cracking.

When the release of pressurethrough valve 15 is not to atmospheric then a suitable pressure on the distillation element 16 is maintained by means of valve 32'loca-tedbeyond the condensing equipment online '30, the necessary valves being also provided on the liquid draw-oft" lines; By varying the pressure on vessel 16 the quantity of vapor evolved and the consequent grade of fuel oil be varied and controlled. The residuum thus formed'is withdrawn through line 17 provided with valve 18. Itwill be understood that heat may be applied in any suitable man- 'ner to the material undergoing vaporization 1n vessel 16 and that 1f desired open steam may also be employed therein to assistin the evolution of the cycle stock vapors and that vacuum may also be employed, if desired.

residuum withdrawn from the system may In the method of the present invention 1' these cycle stock vapors are passed through line 19 thence through a suitable type-of closed, and. preferably insulated, heat exchanger-20, in which they give up a part of their heat. In practice'the temperature ofthe vapors may be'reduced, for example, about 300 F. Consequently, the material flowing through line 19 out of the heater:-

changer 20 will be partly vapor and partly liquid The temperature of this cycle-'stoc is so reduced in the heat exchanger that at 1 the low pressure of the cycle stock it maybe directly contacted with the feed oil to' the system without substantially vaporizing such feed oil. .All of this cyclestock passes into the lower part of a condensation vessel 21,

where the remaining vapors are'condensed by contact with cool feed oilint-roduced, preferably in the form of a spray, through line 22 and valve 23, in the upper portion of the vessel 21. The combined feed stock and condensed cycle stock runsto the bottom of the condensation vessel and is removed through line 25 entering thexsuction side of a pump;

26 by which it is forced through the above described heat exchanger 20in a direction countercurrent to the-flow of hot cycle stock vapors in'line 19. By this means heat transfer is effected from the hotvaporstothe liquid in line 25, raising thetemperature of the latter, and partially vaporizing it.: i The material in line 25, after passing through the exchanger, re-enters'the cracking system at an appropriate point. This may be,for ex ample, the base of the dephlegmatorrfi, in which case it minglcs with the refluxed oil from 6 and is withdrawn throughYlineQS by a pump 29 and forced into the heating coil 1, completingthe cycle. In order. to'bringabout the desired l'efiuxing indephlegmator 6 it may be advisable to divert apart ofthe cold feed oil from 'linef22 through line'27, valve 24, and pump 36 and introduce it, in spray form, into the tower 6 In practice this is found to be quite feasible, since not allgof the feed is required to completely'condense the cycle vapors in the chamber 21.

Instead of using a part of the cold'feed-to reflux cracked vapors as described, it maybe preferable to put the entire amount of feed into the vessel 21, and divide the material in line 25, causing part-of it to flow through the exchanger 20' as shown, and-the remainder to enter the tower 6 through valve 34'and line a '35 as. refluxing agent. Or the entire amount of feedoil may be put-into'the vessel21 and all of the combined feed and cycle stock caused to flow though the exchanger-20.

Upon flowing out of the exchanger it may then-be used asa whole or in part as a refluxing agent inthe tower 6. r

I: Various other modifications fall within the scope of this invention. For example, a part of the condensed naphtha as received intank =9 may be returned to the vapor outlet of the tower 6 through line 33 to assist in fractionacate where tion. Again, the preheated feed and condensedcycle stock in line may be run into line 28 directly, or maybe run into the tower 6 at a point considerably above the base. The temperature of the stock will largely indiit should be returned to the system.

t As an example of the operationof the herein-described'process, Southern California gas T011 w'asheatedin the coil 1 to 860 870 F. The temperature of the vapors out of-the vaporization chambere was'found to be in one case about 340 F., while the temperature of the unvaporized oil from the bottom of 4 was about740 F. A pressure of 275 lbs.

'per square'inch was carried on the system.

Atithe valve '15 this pressure was released to atmospheric. "The vapors leaving the vessel '16 were then at about. 685 -F. In'their passage .through the, exchanger they were cooled toabout 390 F. The feed oil at 70 F. introduced into vessel 21through line 22 condensed all of the cycle stock, and the temperature of the mixed'feed and cycle stock out of vessel 21 was about 150 F. This stock (line 25) was then divided. A part was put 1 into tower 6 and the remainder was passed that of. the residuumtline 17 was 10 A. P. 1., and-that of the naphtha received in through the exchanger 20. In so doing its temperature was raised to about 500F. The combined reflux oil, feed oil'and cycle stock flowing through line 28 .was then found to be about 750 F. It was thus necessary to I raise the temperature of the oil flowing through the coil 1 only 110130 F. An idea of the comparative quantities of oil handled'in his process, in the example H above described may be had from the statement that 13 parts of feed oil per hour were supplied through-line 22, while 30 parts of cycle stock (considered as liquid) per hour passed through line 19, and 200 parts per hour .passedthr'ough line-28 and coil 1. The gravity ofthe feed stock was25 A. P. 1.,

drum 9 was 549 A. P. I. No heat was lost from 'the system except that carried by the residuum flowing through line 17 and that absorbed in condensing the naphtha I (cooler It is to be understood that the ffigures quoted above serve merely to illustrate a typical operation ofthe process, and may vary Widely in other instances. A great deal will depend upon the quality of feed stock used,

the yield and gravity. of naphtha desired and the gravity of residuumrequired.

It ispossiblethat the process-may be operatedto produce along with cycle stock ,vaporssome vapors of naphtha or of an intermediate boiling point oil.'- In the .case of naphtha vapors which are not condensedin vessel 21 it may be preferable to allow them to escape through line 30 and valve 32, leading toa condenser not shown. Such condensed naphtha may'then be run into the body of naphtha coming from the drum 9, or

it may bereturned to an appropriate point in necessary to allow the temperature at the vapor outlet of condensing chamber 21 to .rise. This is accomplished by reducing the amount of feed oil enteringthe chamber through line 22 and valve An advantage of the present process 4 lies in the fact that only one pump .(26) is needed .to recirculate the cycle stock. This pump will be required to handle onlyliquid material and at a moderate temperature.

Another advantage is -derivedirom the" fact that the precooling obtained by cycle a part of thecycle stock. This condensate ,7 runs directly to thebottoni of the vessel 21 and is removed from the condensing chamber thus facilitating the complete condensation of the remaining vapors by the spray of cool feed oil. I

Ifinstead of the closed exchanger shown,

a jet condenser or any. form of direct contact" exchange were employed, a part of the feed oil :and condensed cycle stock would be revaporized and would mingle with the vapors going to the final condenser 21, thus imposing a greater burden upon the condensation operation therein. With apparatus as described, however, the amount of'vaporiza'tion which takes place in the combined feed and cycle stock flowing through line 25 in its passagethrough the heat exchanger 20 is imma-i terial. v y

, It is to be observed that the method of condensation and heat exchange employed in the process of the present invention is appli- 'cable'onlyto materials of the nature of petroleum oi-l, i. e. composed of a number of substanceshaving different 1 boiling points;

It is not applicable to as water (and steam). c

While the form of processherein described pure substances such vapors in the exchanger 20 serves to condense as vapors and part of the oils as liquid, re-

' leasing pressure from said liquid oils and vaporizing therefrom the more volatile con stituents, partially cooling and condensing the vapors to a temperature below that at which said vapors will vaporize substantial portions of fresh feed oil when admixed therewith, by passing the vapors into indirect contact with the cooling medium, then passing such partially cooled and condensed vapors into direct contact with the feed oils of the system so as to further condense the vapors in a zone wherein no substantial vaporization of the feed oil takes place, applying an increased pressure tothe feed oil and comingled condensate, utilizing the feed oil and comingled condensate as a cooling medium in the aforementioned operation of cooling and condensing said vapors, whereby the feed oil and comingled condensate is raised in temperature sufiiciently high to substantially vaporize gas oil unless such increased pressure is imposed thereon, and finally passing the feed oil and comingled condensate tothe' heating zone.

2. A process of decomposing oils into relatively lower boiling point oils which includes, heating the oils to a decomposing temperature, passing the oils into a vaporization chamber under superatmospheric pressure,

removing from said chamber part of the oils as vapors and part of the oils as liquid, releasing pressure from said liquid oils and vaporizing therefrom the more volatile constituents, partially cooling and condensing the latter vapors by subjecting them to indirect contact with the cooling medium, then directly contacting such partially condensed vapors with the feed oils of the system, then applying an increased pressure to the feed oil and comingled condensate, utilizing the feed oil and comingled condensate as a cooling medium in said aforementioned cooling and condensing operation, whereby the feed oil and comingled condensate is raised in temperature sufficiently high to substantially vaporize gas oil unless such increased pressure is imposed thereon, and finally passing the feedoil and comingled condensate to the heating zone.

3. A process of decomposing oils into relatively lower boiling point oils which. includes, heatingflthefoils to a decomposing temperature, passing the oils into" a vaporization chamber under super-atmospheric" pressure, removing from'said chamber part ofthe oils asvapors and part of the oils as liquid, releasingpressure from said liquid oils "and vaporizing therefromthe more volatileconstituents, partially cooling andcondensing said latter vapors by indirect contact-with the cooling medium, then directly contacting the partiallycondensed vapors with the feed oillin the system, utilizing the feed oil comingled with the thuscondensed oils as said cooling medium, whereby the temperature of the feed oil and the thus condensed oils is raised high enough to vaporize gas oil unless additional pressure is imposed thereon, imposing such additional pressure, and passing the feed oil and comingled condensed oil to the heating zone together with any portion of said oils which may be vaporized in said indi rect heat transferring operation. a i I p 1 4. A- process of decomposing oils into relatively lower boiling point oils which includes, hea'ting'the oils to a decomposing tempera: ture, passing the oils into a vaporization chamber under, super-atmospheric pressure, removing from said chambe-ra part at least of the oils as liquid, releasing pressure from said liquid oils and vaporizing therefrom the more volatile T constituents, partially cooling and condensing such vapors by subjecting them in a heat transferring zone to an indirect contact with the cooling medium until theymay be contacted directly with the feed oil of the system without substantially vaporizing such feed;oil,'then passing such partially cooled and condensed vapors into a contacting zone in which they are directly contacted withthe feed oils of the system so as to further'condense the vapors in a zone whereno substantialvaporization of the feed ,oiltakes place, applying an increased pressure tothe feed'oil and commingled condensate, utilizing such ,1 10

commingled feed oil and condensate as a cooling medium in said heat transferring zone, whereby the feed oil and commingled condensate is raised in, temperature sufficiently high to substantially vaporizegas oil unless i such increasedpressure is imposed thereon,

' and passing the feed oil and commingled condensate from said heat transferring zone together wit-h any portion thereof vaporized in said zone to the heating zone.

5. An apparatus fordecomposing oils into i relatively low boiling point oils which comprises,.aheating coil, a vaporization and re action chamber connected to receive oils from said heating 1 coil, means for withdrawing chamber, means for, withdrawing liquids vr1 25 vapors from'said vaporization 'and reaction drawn from saidreaction chamber under 1530 reduced pressure, a heat exchanger receiving said vapors, a contact chamber wherein said Vapors partially condensed from said heat exchanger may be contacted With the feed'oil of the system, means for applying anin crea'sed pressure to the said oil and condensate in said contact chamber and passing the same into said heatexchanger, said heat ex- 16 changer being operative to raise the temperature of the 'feed'oil high enough to vaporize gas oil unless pressure is imposed on the feed oil therein, and means for passing the oils from said heat exchanger to said heating coil.

stituents, partiallycooling saidvapors by indirect contact with the cooling medium in the liquid withdrawn from the vaporization chamber, and finall passing the feed oil and 1 "Signed at San Francisco condensed'oils to t e heati zone.

i hllifornia, this 7th day of September, 192 v ARCHIE L. STROUT.

one heat exchanging zone,then passing the.

vapors to a separate zone in which the vapors are "directly, contacted with feed oil to the 7 system, utilizing the feed oil commingled with the thus condensed oil assaid cooling medium in saidindirect heat exchanging zone, whereby the feedoil and commingled condensed oils are brought to a higher temperature in the indirect heat exchanging zone than in the contacting zone, imposing superatmospheric pressure upon the feed oil and condensed oils before it is passed into the indirect heat exchanging zone, and finally passing the feedoil and condensed oils to the first mentioned heating zone;

' 7 A process of decomposing oils into relatively lower boiling point oils Which includes heating the oils to a decomposing temperature, passing the oil into a vaporization chamber under superatmospheric pressure, removing from said chamber part of the oils as vapors including the produced relatively lower boiling point oils and part of the oils as liquid, releasing pressure from said liquid oil and vaporizing therefrom themore volatile constituents','partially cooling and condensing the latter'vapors by subjecting them to indirect contact with a cooling "medium whereby the same are cooled sufiiciently' so that they may be contacted at atmospheric pressure with the feed oil of the system without materially vaporizing the feed oil, then so contacting said vapors with the feedoils of the system thereby condensing the same, passing feed oils and condensedoils to said 'indirectheat exchanging operation to operate as a cooling medium, superatmospheric 4 7 pressure being imposed thereon, whereby said oils are raised to a higher temperature than the temperature of the oils in the zonejwhe're "the feed oil is contacted with thevapors from V I:

CERTIFICATE OF CORRECTION.

Patent No. 1,834,228. Granted December 1, 1931, to

ARCHIE L. ST ROUT.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 4, line 25, for the numeral "340"read 840; and that theflsaitl Letters Patent should-be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 5th day of April, A. D. 1932.

M. J. Moore, (Seal) Acting Commissioner of Patents. 

